Emergency trip apparatus for a braking system

ABSTRACT

An electric trip switch device for railroad service utilizing a magnetic reed switch in proximity with a permanent magnet, which acts upon the reed switch. A magnetic conductor is adapted to move between the permanent magnet and reed switch in accordance with the actuating mechanism of the trip switch being engaged by a trackside detector to control the reed switch operation. An interlock circuit responsive to the electric signal provided by the reed switch may be employed to control application and release train line wires to produce a trip switch initiated brake application. Reset means comprising an electro-magnet is provided to momentarily reinforce the magnetic field produced by the permanent magnet to initially close the reed switch contacts following a trip switch actuation, after which the contact closure is maintained by the permanent magnet.

United States Patent Sheppard [is] 3,707,627 [451 Dem 26,1972

[54] EMERGENCY TRIP APPARATUS FOR A BRAKING SYSTEM [72] Inventor:Charles W. Sheppard, Trafford, Pa.

[73] Assignee: Westinghouse Air Brake Company,

Wilmerding, Pa. [22] Filed: Dec. 16, 1970 [21] Appl. No.: 98,602

[56] References Cited UNITED STATES PATENTS 3,009,033 11/1961 Werts..335/207 3,319,128 5/1967 Nilssen 1,075,169 7 10/1913 OTHERPUBLICATIONS Funk et al, Variable Mode Pushbutton Switch, IBM TechnicalDisclosure Bulletin, Vol. 6, No. 11 April 1964.

Y APPLICATION WIRE Stadler ..246/200 R x 7 Assistant Examiner-George H.Libman Attorney-Ralph W. Mclntire, Jr.

[57] ABSTRACT An electric trip switch device for railroad serviceutilizing amagnetic reed switch in proximity with a permanent magnet,which acts upon the reed switch. A magnetic conductor is adapted to movebetween the permanent magnet and reed switch in accordance with theactuating mechanism of the trip switch being engaged by a tracksidedetector to control the reed switch operation. An interlock circuitresponsive to the electric signal provided by the reed switch may beemployed to control application and release train line wires to producea trip switch initiated brake application. Reset means comprising anelectro-magnet is provided to momentarily reinforce the magnetic fieldproduced by the permanent magnet to initially close the reed switchcontacts following a trip switch actuation, after which the contactclosure is maintained by the permanent magnet.

6 Claims, 1 Drawing Figure RELEASE WIRE EMERGENCY CONTACTOR I RELEASEWIRE V PATENTED DEC 26 I972 m m m? o w w N U MN WNW 1-; c

m KOPU'QPZOU *UZwOEuEm INVENTOR. CHARLES W SHEPPARD F W M} ATTORNEYEMERGENCY TRIP APPARATUS FOR A BRAKING SYSTEM BACKGROUND OF INVENTIONEmergency trip devices may be either pneumatic or electrical and aretypically employed in railway transit service for automaticallyinitiating a brake application on a vehicle passing over a tracksidedetector device, which may be selectively set up to contact theemergency trip actuating mechanism. The invention relates particularlyto electric type trip switch devices which have the advantage overpneumatic trip devices in that direct interfacing with a conventionalemergency contactor is possible, the emergency contactor being anelectrical interlock device arranged to control the application andrelease train wires, in addition to such other desirable emergencyrelated functions as sanding, horn sounding, etc.

Being mounted on the unsprung portion of the railway vehicle so as toremain properly aligned for engagement with the detector deviceirrespective of the vehicle load condition, however, the trip device iscontinuously subject to vibration and shock forces transmitted from therails during service. Conventional type electrical contacts, which arenormally utilized in electric trip switch devices, are thereforesusceptable to rapid wear by reason of their experiencing a highincidence of arcing encouraged by the vibration tending to open thecontacts. Periodic maintenance is consequently required to maintainelectric trip switches in an operative condition.

SUMMARY OF INVENTION It is therefore the object of the invention toprovide a simple, low-cost, yet reliable electric trip switch devicewhich utilizes a magnetic reed switch, the contacts of which aresubstantially unaffected by car vibration and other environmentalconditions normally associated with'railroad operation.

According to the present invention, there is provided a trip switchdevice having a toggle type trip arm supported at its ends by a membermounted to the car truck and engageable at its hinged midpoint withmeans through'which a ferromagnetic shield is movable within the spaceprovided between a permanent magnet and a magnetic reed switch. When thetrip arm is contacted by a trackside detector, the midpoint of thetoggle is deflected upward, moving the shield between the permanent'magnet and reed switch. The magnetic field flux provided by thepermanent magnet which normally holds the reed switch contacts closed isconsequently shunted away from the reed switch by the highly conductiveshield. In the absence of a magnetic field at the reed switch, itscontacts assume their normally open condition in which anemergencyinterlock circuit controlled by the reed switch is interrupted.

An electro-magnet is provided to reset the reed switch contacts.Momentary energization of the electro-magnet, after the trip arm resets,establishes a flux field which reinforces the permanent magnet fluxfield so that the combined flux density influencing the reed switch issufficient to produce closure of the reed switch contacts and therebycomplete the previously interrupted emergency interlock circuit. Oncethe contact closure is accomplished, the electro-magnet may bedeenergized and the permanent magnet alone will hold in the reedcontacts to maintain circuit continuity until the trip switch issubsequently actuated.

Other objects, features and attendant advantages will become morereadily apparent from the following detailed description when consideredin conjunction with the accompanying single FIGURE drawing of anillustrative embodiment of the invention in which the disclosed tripswitch device is shown diagrammatically, partly in outline and partly inelevation section.

Referring now to the drawing, a trip switch device 1 comprises a tripmechanism2 which includes a pair of relatively wide cooperating armsegments 3 and 4, the outer ends of which are each provided with a pin5. Elongated slots 6 are formed in a mounting bracket 7 to receive pins5 and thereby support the outer ends of arm segments 3 and 4. The slots6 accommodate longitudinal movement of the arm ends relative to bracket7, which is secured by bolts 8 to the truck frame 9 or other suitableunsprung portion of a railway vehicle with whichthe trip switch device 1is associated. The inner end of one of the arm segments 3 or 4 isarranged with a clevis and is joined by a wristpin 10 to the adjoiningarm segment to provide a hinged joint connection at the midpoint of tripmechanism 2.

Also included in trip mechanism 2 is a follower stem 11 having a springseat 12 formed integral, or otherwise secured therewith, and adapted toengage arm segments 3 and 4 near their hinged midpoint.

Further comprising trip switch device 1, in addition to trip mechanism 2is a magnetic switch assembly 13, the body of which is formed of amagnetic insulator material. Assembly 13 is clamped or bolted to themounting bracket 7 so that a bore 14 therein, in which stem 11 operates,is aligned vertically above the midpoint of arms 3 and 4.

Carried in assembly 13 is a conventional magnetic reed type switch 15arranged in spaced-apart relation with a permanent magnet 16, the polesof which are located so as to polarize the normally open reed switchcontacts and thereby establish a magnetic force of attractiontherebetween. The reed switch is mounted with its contacts disposed soas to operate in a horizontal plane contrary to the direction ofvibration forces, the effects of which are thereby minimized. Amagnetically conductive shield 17 formed of a ferromagnetic material issuitably attached to the end of stem 11 opposite the end with which thehinged joint connection of trip mechanism 2 is engaged. Disposed aboutstem 1 1 is a spring 18 caged between spring seat member 12 and anannular recess formed in the bottom of unit 13. Trip mechanism 2 isurged downward at the hinged joint connection of arms 3 and 4 by spring18 acting through seat 12 so as to be disposed in a depending position.As shown in the drawing, stem 11 is positioned in bore 14 such thatshield 17 is removed-from the space between the reed switch 15 andpermanent magnet 16. The normal depending position of the trip mechanism2 including location of stem 1 1 in bore 14 is defined by reason of thepin 5 in each armsegment 3 and 4 engaging the one extreme end of therespective elongated slots 6. A trackbed mounted detector device arailway vehicle, on which the trip switch 1 is mounted, passing over thedetector. A wheel 20 is preferably provided with the detector 19toeffect friction free engagement thereof with arm segment 3 or 4 of thetrip mechanism 2, depending upon the direction of vehicle travel.

Also carried in assembly 13 is an electro-magnet 21, energization ofwhich is controlled by a spring-loaded reset switch 22. A pole piece 23,forming the core of the electromagnet, is located relative to the polesof permanent magnet 16 so that their magnetic flux fields interact in areinforcing manner. The combined flux density of the interacting fieldsproduces sufficient magnetic attraction between the reed switch contactsto overcome the contact tension and thereby establish contact closure.The strength of permanent magnet 16 and its proximity with reed switchare selected so that the effective magnetic energy is insufficient toclose the reed switch contacts, but is sufficient to maintain thecontacts in a closed condition subsequent to their being initiallyclosed by the supplemental effect produced by the electro-magnet.

A conventional emergency contactor device, as represented by block 24,is shown as illustrative of means responsive to the signal provided bythe reed switch operation for producing a brake application. Typically,the emergency contactor is utilized as an electrical interlock providingcontrol of the application and release train wires in accordance withthe condition of the reed switch, as hereinafter explained.

In describing the operation of trip switch device 1, let it be assumedthat the contacts of the reed switch 15 are maintained in a closedcondition by the effects of permanent magnet 16 to complete a circuit tothe emergency contactor device 24. Being normally arranged in afail-safe configuration, interlock circuitry provided by the emergencycontactor establishes nor- I mal control of the application and releasetrain wires by the operator. The field strength of the permanent magnetproduces sufficient magnetic attraction between the reed switch contactsto maintain the contacts ina closed state during service against theeffective contact tension and vibration forces tending to separate thecontacts.

When it is desired to automatically stop an approaching railway vehicleor train on which the trip switch 1 is mounted, in the event theoperator should fail, for example, to heed a warning signal to stop thevehicle or train, or for any reason is delinquent in bringing thevehicle or train to a halt at a prescribed location, it is simplynecessary to set up an appropriately located detector device, such asdetector 19 to strike the trip mechanism 2 of the trip switch 1, as thevehicle or train passes the detector.

In passing the detector 19, one of the arm segments 3 or 4 of trip lever2 is carried over the detector wheel 20, thereby resulting in themidpoint of trip mechanism 2 being deflected upward against spring 18,which is compressed between the body of assembly 13 and spring seatmember 12. Slots 6 in bracket 7 accommodate outward movement of the endsof arm segments 3 and '4, as the midpoint is shifted upward. In beingdeflected upward, the hinged midpoint of arms 3 and 4 act through seatmember 12, forcing stem 11 upward in bore 14 a distance sufficient tolocate shield 17 in the space between the reed switch 15 and permanentmagnet 16. Being of a ferromagnetic material, shield 17 serves thepurpose of readily conducting the permanent magnet field flux under theinfluence of which the reed switch contacts are normally maintainedclosed. This is accomplished by reason of the magnetic field fluxproduced by the permanent magnet having a propensity for theferromagnetic material of which the shield 17 is formed so that thefield tends to be shunted away from reed switch 15 via shield 17,substantially reducing formation of a field at the reed switch. As aresult insufficient energy is available to maintain the reed switchcontacts closed against the contact tension and the contactsconsequently drop out to break the circuit to the emergency contactor24.

The length of the arm segments 3 and 4 is chosen in accordance with theresponse time of the reed switch and anticipated maximum speed at whicha vehicle can be expected to pass over the detector device 19, in orderto assure that the shield 17 remains effective to shunt the permanentmagnet field away from, reed switch 15 for a duration sufficient topermit contact dropout to occur before the trip lever is reset. Once thereed switch contacts are open, shield 17 is withdrawn from the spaceseparating the reed switch and permanent magnet by reason of the hingedmidpoint of arms 3 and 4 passing over the detector wheel 19 so thatspring 18 is effective to return the trip lever to its normal dependingposition. With shield 17 withdrawn, the

magnetic field is able to expand sufficiently to encompass the magneticreed switch. Since the energy of the field produced by the permanentmagnet without the field effect of electro-magnet 21 is insufficient toeffect contact closure, the circuit to the emergency contact 25 willremain open, even after the trip mechanism resets.

In consequence of the reed switch being open, emergency contactor 24 iscaused to establish circuitry whereby the application train wire isenergized to produce a brake application and the release train wire isinterrupted to prevent brake release until such time as the reed switch15 is reset to its closed condition.

After the vehicle or train is stopped following the trip switchinitiated brake application, switch 22, which may be convenientlylocated in the operators cab, is operated to energize the electro-magnet21. With shield 17 removed from the space between the permanent magnetand reed switch, and with electro-magnet 21 energized, sufficientmagnetic energy is effective to reset the reed switch contacts to aclosed condition. This reestablishes circuit continuity to the emergencycontactor to restore the interlock circuitry thereof to'a condition inwhich control of the brakes is provided through the train wires in thenormal manner.

Reliable operation of the trip switch is thus assured by its simplicityof structure and its unique operating muno HA1 a. magneticallyresponsive switch means for providing said indication when operated froma closed condition to a normally open condition,

b. a permanent magnet spaced from said switch means a distancesufficient to prevent the magnetic faces of said permanent magnet fromoperating said switch'means to said closed condition and to permit themagnetic forces of said permanent magnet to maintain said switch meansin said closed condition following operation thereto,

c. a selectively operable electro-magnet arranged in reinforcingrelationship with said permanent magnet to effect in cooperationtherewith actuation of said switch means to said closed position, and

d. actuator means including a magnetically conductive shield memberoperative in response to en- I gagement of said actuator means with saiddetector for movement into the space separating said switch means fromsaid permanent magnet, thereby to direct the magnetic forces thereofaway from said switch means to allow said switch means to assume saidnormally open condition.

2. The apparatus, as recited in claim 1, wherein said electro-magnet iseffective to maintain said switch means in said closed condition only solong as the magnetic force provided by said permanent magnet iseffective to act upon said switch means.

3. The apparatus, as recited in claim 1, wherein said switch means is areed relay disposed in such an attitude that the reed contacts thereofoperate in a horizontal direction to effect said open and closedconditions.

4. The apparatus, as recited in claim 1, wherein said actuator meansfurther includes a trip lever having a hinged midpoint formed by theadjoining ends'of outwardly extending arm segments, the opposite ends ofwhich are pivotally carried by a support member attached to said vehicleto permit displacement of the hinged midpoint from a normal dependingposition to an actuated position responsive to engagement with saiddetector device, said shield member being engageable with the hingedmidpoint for movement therewith into the space separating said switchmeans from said permanent magnet.

5. The apparatus, as recited in claim 4, wherein said actuator meansfurther comprises:

a. a follower engageably disposed between the midpoint of said triplever and said magnetically conductive shield member, and

b. spring means disposed between said support member and said followerfor urging said hinged midpoint toward said normal depending position.

6. The apparatus, as recited in claim 4, wherein said support member isprovided with elongated slots in which the ends of said arm segmentsopposite said hinged midpoint are supported for limited movement todefine said depending position thereof.

1. Emergency trip switch apparatus mountable on a railway vehicle forengagement with a trackway detector device to provide an indication ofthe vehicle passing the detector, said apparatus comprising: a.magnetically responsive switch means for providing said indication whenoperated from a closed condition to a normally open condition, b. apermanent magnet spaced from said switch means a distance sufficient toprevent the magnetic faces of said permanent magnet from operating saidswitch means to said closed condition and to permit the magnetic forcesof said permanent magnet to maintain said switch means in said closedcondition following operation thereto, c. a selectively operableelectro-magnet arranged in reinforcing relationship with said permanentmagnet to effect in cooperation therewith actuation of said switch meansto said closed position, and d. actuator means including a magneticallyconductive shield member operative in response to engagement of saidactuator means with said detector for movement into the space separatingsaid switch means from said permanent magnet, thereby to direct themagnetic forces thereof away from said switch means to allow said switchmEans to assume said normally open condition.
 2. The apparatus, asrecited in claim 1, wherein said electro-magnet is effective to maintainsaid switch means in said closed condition only so long as the magneticforce provided by said permanent magnet is effective to act upon saidswitch means.
 3. The apparatus, as recited in claim 1, wherein saidswitch means is a reed relay disposed in such an attitude that the reedcontacts thereof operate in a horizontal direction to effect said openand closed conditions.
 4. The apparatus, as recited in claim 1, whereinsaid actuator means further includes a trip lever having a hingedmidpoint formed by the adjoining ends of outwardly extending armsegments, the opposite ends of which are pivotally carried by a supportmember attached to said vehicle to permit displacement of the hingedmidpoint from a normal depending position to an actuated positionresponsive to engagement with said detector device, said shield memberbeing engageable with the hinged midpoint for movement therewith intothe space separating said switch means from said permanent magnet. 5.The apparatus, as recited in claim 4, wherein said actuator meansfurther comprises: a. a follower engageably disposed between themidpoint of said trip lever and said magnetically conductive shieldmember, and b. spring means disposed between said support member andsaid follower for urging said hinged midpoint toward said normaldepending position.
 6. The apparatus, as recited in claim 4, whereinsaid support member is provided with elongated slots in which the endsof said arm segments opposite said hinged midpoint are supported forlimited movement to define said depending position thereof.